linux-kernel - Re: [PATCH v6 4/5] dt-bindings: phy: realtek: Add the doc about the Realtek SoC USB 2.0 PHY

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Date:   Fri, 30 Jun 2023 19:21:49 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Stanley Chang[昌育德] 
        <stanley_chang@...ltek.com>
Cc:     Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Flavio Suligoi <f.suligoi@...m.it>,
        Ray Chi <raychi@...gle.com>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v6 4/5] dt-bindings: phy: realtek: Add the doc about the
 Realtek SoC USB 2.0 PHY

On Fri, Jun 30, 2023 at 07:33:45AM +0000, Stanley Chang[昌育德] wrote:
> Hi Rob,
> 
> > On Thu, Jun 29, 2023 at 01:45:12PM +0800, Stanley Chang wrote:
> > > Add the documentation explain the property about Realtek USB PHY driver.
> > 
> > In the subject, drop "the doc about the". It's redundant. And perhaps add 'DHC
> > RTD SoC' if this isn't for *all* Realtek SoCs.
> > 
> > > Realtek DHC (digital home center) RTD SoCs support DWC3 XHCI USB
> > > controller. Added the driver to drive the USB 2.0 PHY transceivers.
> > 
> > driver? This is a binding for the h/w.
> 
> I mean, the driver is drivers/phy/realtek/phy-rtk-usb2.c
> I will revise as
>     dt-bindings: phy: realtek: Add the Realtek DHC RTD SoC USB 2.0 PHY
> 
>     Add the documentation explain the property about Realtek USB PHY driver.
> 
>     Realtek DHC (digital home center) RTD SoCs support DWC3 XHCI USB
>     controller and uses phy-rtk-usb2 as driver for USB 2.0 PHY transceiver..

No, you should mention nothing to do with how a particular operating
system chooses to structure its code here. Bindings describe hardware,
and the commit message should reflect that.

> 
> > > +$id: http://devicetree.org/schemas/phy/realtek,usb2phy.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Realtek DHC SoCs USB 2.0 PHY
> > > +
> > > +maintainers:
> > > +  - Stanley Chang <stanley_chang@...ltek.com>
> > > +
> > > +description:
> > 
> > You need '|' if formatting (line breaks) are important.
> 
> I think I need it. I will add it.
> 
> > > +  realtek,inverse-hstx-sync-clock:
> > > +    description:
> > > +      For one of the phys of RTD1619b SoC, the synchronous clock of the
> > > +      high-speed tx must be inverted.
> > 
> > "invert" assumes I know what non-inverted means. I do not. Better to state in
> > terms of active high, low, falling edge, rising edge, etc.
> 
> Meaning, the clock must be reversed.

Maybe that means something to Rob, but "reversed" doesn't seem any more
meaningful than inverse. I agree that it should be described in terms of
"active high" etc, as they have well understood meanings.

> > > +    type: boolean
> > > +
> > > +  realtek,driving-level:
> > > +    description:
> > > +      Control the magnitude of High speed Dp/Dm output swing.
> > > +      For a different board or port, the original magnitude maybe not
> > meet
> > > +      the specification. In this situation we can adjust the value to meet
> > > +      the specification.
> > 
> > What are the units?
> 
> There is no unit. It is only a gain for adjusting the magnitude.

Gain has units too.

> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    default: 8
> > > +    minimum: 0
> > > +    maximum: 31
> > > +
> > > +  realtek,driving-compensate:
> > 
> > compensate what?
> 
> It is to compensate the driving level.

Should it be called "driving-level-compensate" then?

> In other word, to adjust the driving level.

So, "realtek,driving-level" sets the gain and
"realtek,driving-compensate" adjusts the driving level.
By that logic, is this also a gain?

Also this property is only for the RTD1315e? That should be
described in/constrained by the binding itself, not in the text
description alone IMO.


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